The posterior segment (i.e. behind the natural lens) of the eye is filled with a jellylike substance called the vitreous. It may be necessary to remove damaged vitreous as part of eye surgery. An eye surgery operation performed to remove vitreous is called vitreous surgery (vitrectomy). When the vitreous is removed, the body quickly replaces it with a substitute clear liquid.
A surgical instrument used in vitreous surgery typically is a hand-held vitreous cutter comprising a probe that is inserted into the eye through an incision and includes a tube which draws in a portion of vitreous. The probe also includes a cutting mechanism which severs vitreous, allowing vitreous to be drawn out through the tube by suction.
The probe generally consists of a concentric arrangement of an inner tube driven by an actuator in an outer tube, with the outer tube extending distally beyond the inner tube. The outer tube has an opening at or near its distal tip. When suction is applied to the inner tube, a portion of vitreous is pulled into the opening of the outer tube. When the inner tube is then driven axially forward by the actuator, it shears off the vitreous portion projecting through the opening in the outer tube. The vitreous material is then aspirated through the inner tube by a suction source.